Most DSA switch tags shift the EtherType to the right, causing the
master to not parse the VLAN as VLAN.
However, not all switches do that (example: tail tags, tag_8021q etc),
and if the DSA master has "rx-vlan-filter: on" in ethtool -k, then we
have a problem.

Therefore, we could populate the VLAN table of the master, just in case
(for some switches it will not make a difference), so that network I/O
can work even with a VLAN filtering master.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>